Cannula for a medical or dental-medical handpiece used for spraying an abrasive flow medium

Abstract

The invention relates to a cannula for a medical or dental-medical handpiece for spraying a flow medium which contains abrasively effective particles, having a cannula shaft which is in substance straight, and a sideways directed outlet nozzle in the forward end region of the cannula shaft, wherein in the cannula shaft a first channel section of a delivery line extends axially forwardly, from which there extends a second channel section sideways to the outlet nozzle. In order to increase the working life, in the region of the apex of the angle included by the channel sections there is arranged an impact wall lying axially opposite to the first channel section, and/or the channel sections are surrounded by a protective wall at least over a part of their length, wherein the impact wall and/or the protective wall are of a material that is more wear resistant or harder than the material of the cannula shaft.

1 . Cannula for a medical or dental-medical handpiece for spraying a flow medium that contains abrasively effective particles, comprising 
 a cannula foot,    a cannula shaft extending substantially straight forwardly from the cannula foot and having a forward end region and a rearward end region,    an outlet nozzle in the forward end region of the cannula shaft, directed sideways therefrom,    a first channel section of a first delivery line extending axially forwardly in the cannula shaft,    a second channel section extending sideways from the first channel section to the outlet nozzle,    a second delivery line extending in the cannula from an inlet opening in the region of the cannula foot, and,    a first channel section of the second delivery line extending forwardly substantially parallel to the first channel section of the delivery line over a first length section in the rearward end region,    wherein,    the second delivery line ( 21 ) extends to a ring nozzle surrounding the second channel section of the first delivery line in the region of the outlet nozzle ( 4 ), and    wherein the first channel section of the second delivery line is formed by a ring gap which surrounds a straight channel sleeve emplaced in the cannula shaft and forming the first channel section, and is connected in a forward end region thereof with the ring nozzle by means of at least one continuing connection channel.    
     
     
         2 . Cannula according to  claim 1 , 
 wherein,    the channel sleeve continuously tapers in a ring-shape forwardly from its rearward end region to form the ring gap.    
     
     
         3 . Cannula according to  claim 1 , 
 comprising,    a return flow blocking valve disposed in the second delivery line.    
     
     
         4 . Cannula according to  claim 3 , 
 wherein    the return flow blocking valve is a membrane valve or a lip valve.    
     
     
         5 . Cannula according to  claim 3 , 
 wherein    the return flow blocking valve is arranged in one or both of the region of the outlet nozzle and a middle region of the cannula.    
     
     
         6 . Cannula according to  claim 4 , 
 wherein,    the return flow blocking valve has a ring-like membrane with an inner or outer edge axially fixed and the respective other edge cooperates sealingly with a ring surface and is a axially elastically bent outwardly through the flow pressure of the flow medium.    
     
     
         7 . Cannula according to  claim 3 , wherein, 
 the return flow blocking valve is accessible from the rear in a rearward recess.    
     
     
         8 . Cannula according to  claim 3 , 
 wherein,    the continuing connection channel has a transverse channel extending from a forward end region of the ring gap.    
     
     
         9 . Cannula according to  claim 8 , 
 wherein,    the second delivery line has a delivery line section extending forwardly from a transverse channel and axis-parallel with reference to the first channel section of the first delivery line.    
     
     
         10 . Cannula according to  claim 9 , 
 wherein    the return flow blocking valve is arranged in the delivery line section.    
     
     
         11 . Cannula according to  claim 10 , 
 wherein,    the delivery line section is accessible from the rear.    
     
     
         12 . Cannula according to  claim 11 , 
 wherein    the return flow blocking valve an be introduced and exchanged from the rear.    
     
     
         13 . Cannula according to  claim 15 , 
 wherein,    the closure part is releasably connected with the cannula from the rear.    
     
     
         14 . Cannula according to  claim 1 , 
 wherein    the outlet nozzle has a nozzle sleeve surrounded by the ring nozzle, which is sunken in an annex of the cannula standing out to the side.    
     
     
         15 . Cannula according to  claim 7 , wherein the rearward recess is closed by a closure part.  
     
     
         16 . Cannula according to  claim 13 , wherein the closure part is releasably connected with the cannula by means of a quick-fastening connection device.